This wave of "cyber-flashing" is made possible by AirDrop's receiving settings -- you can receive from everyone, no one, or just your contacts. As Gothamist reports, "some people don't realise they have their phones set to receive AirDrops from 'Everyone', and that's what the perverts, who can send photos to anyone with that setting within Bluetooth range, are taking advantage of."

To make sure your phone is safe, swipe up from the bottom of your phone to open the control center. (If you keep Bluetooth off, you're in the clear.)

If you're in NSW, you can call 131 444 to report sexual misconduct to the police. In other states, check with your local police.